Good going ivylass.
Nicely handled.
I have thought of another source of educational material.
If somebody has already mentioned it, then sorry, but it’s worth mentioning again.
There are many more magazines available for teenage girls than teenage boys.
They are age appropriate, and usually have a “wait til you’re legally above the age of consent, and both emotionally ready” stance, while still talking honestly (and non-judgementally) about topics that are a little off the beaten track; oral sex, homosexuality, masturbation etc.
In the UK the titles I’d be thinking of would include J-17, Bliss, Sugar, Cosmo girl, Elle girl and so on. Perhaps you could investigate similar titles?
You can flick through a couple and see which ones you feel happiest about. There is the added advantage of having no pornographic content, and also providing him with some insight into what girls REALLY think. 
In my experience our magazines would always be stolen by boys wanting to read the problem pages…
Keep him away from FHM etc.
Their style is a very tongue-in-cheek misogyny, very laddish, not really what you want.
Although I don’t find the sex advice to be anywhere NEAR as graphic as the average Cosmo.
Whether you want to just say
“Oh dear, I meant to buy cosmo and picked this up instead”,
and leave it lying around,
or whether you want to actually hand it to him with a
“Well if you’re getting into girls, you might want some insider info”
type comment, is up to you.
BTW headchecked, “if your child is prone to sex” is the funniest thing i’ve read all day.
sorry.
i’m not poking fun, it was just an odd word choice, which made me chuckle.